58 A MANUAL OF ANATOMY. 



which are separated by the nasal nerve. These branches 

 run forward between the two heads of the external rectus. 

 The superior division of the third nerve. This is the 

 smallest ; it passes forward and inward over the optic nerve 

 to the rectus superior and levator palpebrae superioris. The 

 lower division is the larger and divides into three branches, 

 one to the rectus internus, another to the rectus inferior, 

 the third to the obliquus inferior. From this last branch 

 the motor root of the ophthalmic ganglion arises. 



Rectus Inferior. 



Origin. From the lower margin of the optic foramen. 



Insertion. Into the lower part of the sclerotic coat of the 

 eye just behind the corneal margin. 



Nerve Supply. The inferior branch of the third nerve. 



Action. To depress and at the same time slightly rotate 

 and draw the cornea inward. 



Obliquus Inferior. 



Origin. From the front of the orbital cavity at the j unc- 

 tion of its lower and inner surfaces, just outside the opening 

 of the nasal duct. 



Insertion. Into the outer posterior part of the eye-ball 

 under the external rectus. 



Nerve Supply. The third or motor-oculi through the in- 

 ferior branch. 



Action. To rotate the cornea outward, and to turn the 

 eye-ball slightly upward and outward. 



DISSECTION. 



If the skull has been opened, the brain removed, the interior of the base of 

 the skull dissected, and the orbit finished, then take up the dissection of the 

 face. 



Nothing upon the face has been dissected except the orbicularis palpebra- 

 rum. The structures are covered by a layer of fascia and the upward projec- 

 tion of the platysma. 



